A number of products are available or described for displaying either two dimensional (2D) or three dimensional (3D) images. For viewing 2D images or videos, CRT (cathode ray tube) monitors, LCD (liquid crystal display), OLED (organic light emitting diode) displays, plasma displays, and projection systems are available. In these systems, both human eyes are essentially viewing the same image.
To achieve the impression of 3D, each of the pair of human eyes must view a different image (i.e. captured from a different physical position). The human visual system then merges information from the pair of different images to achieve the impression of depth. The presentation of the pair of different images to each of a pair of human eyes can be accomplished a number of ways, sometimes including special 3D glasses (herein also referred to as multi-view glasses or stereo glasses) for the viewer.
In general, multi-view glasses contain lens materials that prevent the light from one image from entering the eye, but permit the light from the other. For example, the multi-view glasses permit the transmittance of a left eye image through the left lens to the left eye, but inhibit the right eye image. Likewise, the multi-view glasses permit the transmittance of a right eye image through the right lens to the right eye, but inhibit the left eye image. Multi-view glasses include polarized glasses, anaglyph glasses, and shutter glasses.
Anaglyph glasses refer to glasses containing different lens material for each eye, such that the spectral transmittance to light is different for each eye's lens. For example, a common configuration of anaglyph glasses is that the left lens is red (permitting red light to pass while blue light is blocked) and the right lens is blue (permitting blue light to pass while red light is blocked). An anaglyph image is created by first capturing a normal stereo image pair. A typical stereo pair is made by capturing a scene with two horizontally displaced cameras. Then, the anaglyph is constructed by using a portion of the visible light spectrum bandwidth (e.g. the red channel) for the image to be viewed with the left eye, and another portion of the visible light spectrum (e.g. the blue channel) for the image to be viewed with the right eye.
Polarized glasses are commonly used for viewing projected stereo pairs of polarized images. In this case, the projection system or display alternately presents polarized versions of left eye images and right eye images wherein the polarization of the left eye image is orthogonal to the polarization of the right eye image. Viewers are provided with polarized glasses to separate these left eye images and right eye images. For example, the left image of the pair is projected using horizontally polarized light with only horizontal components, and the right image is projected using vertically polarized light with only vertical components. For this example, the left lens of the glasses contains a polarized filter that passes only horizontal components of the light; and the right lens contains a polarized filter that passes only vertical components. This ensures that the left eye will receive only the left image of the stereo pair since the polarized filter will block (i.e. prevent from passing) the right eye image. This technology is employed effectively in a commercial setting in the IMAX system.
One example of this type of display system using linearly polarized light is given in U.S. Pat. No. 7,204,592 (O'Donnell et al.). A stereoscopic display apparatus using left- and right-circular polarization is described in U.S. Pat. No. 7,180,554 (Divelbiss et al.).
Shutter glasses, synchronized with a display, also enable 3D image viewing. In this example, the left and right eye images are alternately presented on the display in a technique which is referred to herein as “page-flip stereo”. Synchronously, the lenses of the shutter glasses are alternately changed or shuttered from a transmitting state to a blocking state thereby permitting transmission of an image to an eye followed by blocking of an image to an eye. When the left eye image is displayed, the right glasses lens is in a blocking state to prevent transmission to the right eye, while the left lens is in a transmitting state to permit the left eye to receive the left eye image. Next, the right eye image is displayed with the left glasses lens in a blocking state and the right glasses lens in a transmitting state to permit the right eye to receive the right eye image. In this manner, each eye receives the correct image in turn. Those skilled in the art will note that projection systems and displays which present alternating left and right images (e.g. polarized images or shuttered images) need to be operated at a frame rate that is fast enough that the changes are not noticeable by the user to deliver a pleasing stereoscopic image. As a result, the viewer perceives both the left and right images as continuously presented but with differences in image content related to the different perspectives contained in the left and right images.
Other displays capable of presenting 3D images include displays which use optical techniques to limit the view from the left eye and right eye to only portions of the screen which contain left eye images or right eye images respectively. These types of displays include lenticular displays and barrier displays. In both cases, the left eye image and the right eye image are presented as interlaced columns within the image presented on the display. The lenticule or the barrier act to limit the viewing angle associated with each column of the respective left eye images and right eye images so that the left eye only sees the columns associated with the left eye image and the right eye only sees the columns associated with the right eye image. As such, images presented on a lenticular display or a barrier display are viewable without special glasses. In addition, the lenticular displays and barrier displays are capable of presenting more than just two images (e.g. nine images can be presented) to different portions of the viewing field so that as a viewer moves within the viewing field, different images are seen.
Some projection systems and displays are capable of delivering more than one type of image for 2D and 3D imaging. For example, a display with a slow frame rate (e.g. 30 frames/sec) can present either a 2D image or an anaglyph image for viewing with anaglyph glasses. In contrast, a display with a fast frame rate (e.g. 120 frames/sec) can present either a 2D image, an anaglyph image for viewing with anaglyph glasses or an alternating presentation of left eye images and right eye images which are viewed with synchronized shutter glasses. If the fast display has the capability to present polarized images, then a wide variety of image types can be presented: 2D images, anaglyph images viewed with anaglyph glasses, alternating left eye images and right eye images that viewable with shutter glasses or alternating polarized left eye images and polarized right eye images that are viewable with glasses with orthogonally polarized lenses.
Not all types of images can be presented on all projection systems or displays. In addition, the different types of images require different image processing to create the images from the stereo image pairs as originally captured. Different types of glasses are required for viewing the different types of images as well. A viewer using shutter glasses for viewing an anaglyph image would have an unsatisfactory viewing experience without the impression of 3D. Further complicating the system is that particular viewers have different preferences, tolerances, or abilities for viewing “3D” images or stereo pairs, and these can even be affected by the content itself.
Certain displays are capable of both 2D and 3D modes of display. To make a display capable of 2D or 3D operation, prior art systems require removal of the eyeglasses and manual switching of the display system into a 2D mode of operation. Some prior art systems, such as U.S. Pat. No. 5,463,428 (Lipton et al.) have addressed shutting off active eyeglasses when they are not in use, however, no communications are made to the display, nor is it then switched to a 2D mode. U.S. Pat. No. 7,221,332 (Miller et al.) describes a 3D display switchable to 2D but does not indicate how to automate the switchover. U.S. Patent Application Publication No. 2009/0190095 describes a switchable 2D/3D display system based on eyeglasses using spectral separation techniques, but again does not address automatic switching between modes. In U.S. Ser. No. 12/245,059, there is described a system including a display and glasses where the glasses transmit a signal to the display to switch to 2D mode when the glasses are removed from the face.
Viewing preferences are addressed by some viewing systems. For example, in U.S. Ser. No. 12/212,852, the viewing population is divided into viewing subsets based on the ability to fuse stereo images at particular horizontal disparities and the stereo presentation for each subset is presented in an optimized fashion for each subset. In U.S. Pat. No. 7,369,100, multiple people in a viewing region are found, and viewing privileges for each person determine the content that is shown. For example, when a child is present in the room, only a “G” rated movie is shown. In U.S. Patent Application Publication No. 2007/0013624, a display is described for showing different content to various people in the viewing region. For example, a driver can see a speedometer, but the child in the passenger seat views a cartoon.